I use the tree spurs for cottonweed, elm, ash... thick barked stuff. I switch to pole gaffs for silver maple, birch, sycamore and other thinner barked stuff. The tree spurs, in harder woods can cause a lot of pressure on your tibia, which can get painful pretty quick, especially with pads that have metal cups going around your shin. Pole spurs, your feet are tighter to the tree, so that's not an issue. It takes me a few minutes to swap the spurs out if I need to do it on the jobsite.
With my climbers, I'm using Mike's Powerscender set. With the pole spurs, the ascender takes a real beating on the tree, so if you're using a spur ascender, that might be an issue. With the tree spurs, I don't have that problem.